The invention relates generally to automatic test equipment and more particularly a device-under-test (DUT) power supply for use with a semiconductor tester.
Automatic test equipment (ATE) provides the ability for semiconductor device manufacturers to test each and every device fabricated. This enables the manufacturer to prevent defective devices from entering the marketplace, thereby maximizing quality and reliability. Not surprisingly, this correspondingly translates to higher product revenues. With the complexity and sophistication of todays modern semiconductor devices, ATE in a semiconductor manufacturing plant is a necessity in order for the manufacturer to remain competitive.
Conventional ATE typically provides power supplies to supply power to a device-under-test (DUT). Given that a semiconductor tester may be used to test a wide range of devices, the current required may vary over a wide range. Further, there may be cases where a tester user may want to test several devices in parallel. This combination of requirements is frequently addressed by designing a number of power supplies, each having the ability to generate some small current. These supplies are often designed so they can be paralleled to produce a smaller number of higher power supplies.
Paralleling a large number of power supplies often encounters several problems, including unequal current sharing, inaccuracies in summed current measurements and current clamping, and undesirable circuit complexities at the power supply output. Because accuracy requirements for DUT power supplies are generally couched in terms of output voltage and current, minimizing any adverse effects at the output is highly desirable.
What is needed and heretofore unavailable is a high-accuracy device power supply for ATE applications capable of addressing the paralleling problems noted above. The modular ATE power supply architecture of the present invention satisfies this need.
The modular ATE power supply architecture of the present invention provides a modular way to scale the output of a DUT power supply with minimal circuit complexity in the output stages. This allows for straightforward parallel configurations that are easily controllable and highly accurate.
To realize the foregoing advantages, the invention in one form comprises a modular power supply architecture for automatic test equipment. The power supply architecture includes a control module having a pair of control signal output lines and a plurality of output modules. The control module includes control circuitry to generate control signals along the control signal output lines and measurement circuitry coupled to the control signal output lines. The output modules have respective control inputs coupled in parallel to the control signal output line to receive the control signals and respective current outputs connected in parallel. The output modules are operative in response to the control signals to generate respective currents at the current outputs. A current output bus receives and sums the respective current outputs, the output bus being isolated from the control signal line.
In another form, the invention comprises a method of supplying power to a device-under-test. The method includes the steps of selecting a control module comprising control circuitry for generating respective sink and source control signals along respective source and sink control lines; paralleling a plurality of output current modules to receive the sink and source control signals from the respective source and sink control lines; summing the output currents from the output current modules to an output current bus; and isolating the output current bus from the control circuitry. Any control section can drive any number of output sections, said output sections may or may not be of equal current capability. The total output current capability of the power supply created by the combination of elements is just the total of the paralleled output sections, and the total transconductance is the sum of transconductances of those output sections.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.